The invention generally relates to audio/video management systems, including announcement control systems. More particularly, the invention relates to an electronic end-of-line module used in audio/video management systems to facilitate testing, monitoring and detection in such systems. Publicly accessible areas are often equipped with broadcasting systems having both audio and video components for disseminating information to the general public. For example, museums, stadiums, casino and other resorts, hospitals, theme parks, factories, military installations, shopping centers, train stations, bus stations, airports, and smaller facilities, including grocery stores, have audio/video announcement systems. Announcement control systems may include, for example, the following components or sub-systems, monitoring and testing, DSP (digital signal processing) processing, power amplification, backup, computerized communications, and flight, courtesy, and/or visual announcement systems. Moreover, an announcement control system may receive inputs from devices such as microphones, telephones, and music sources and may be integrated, to varying degrees, with other networked or stand-alone systems, e.g., fire alarm system, either directly or by use of a network switching device.
In transportation centers, automated and real-time audio announcements are a necessity for informing travelers of arrival and departure times, paging messages, emergency announcements, gate or terminal changes, and a host of other messages necessary to facilitate efficient travel. It is essential that audio delivery equipment, such as speakers, audio input/output control, processing and distribution equipment, and associated wiring, are in proper working order to insure travelers and other persons of interest, depending on the facility, are effectively informed of important information. For example, when a flight schedule is modified, a video display device displaying information for multiple flights will often simply change the affected flight information on the display. Often, a concomitant audio announcement is made to inform passengers that a particular flight has been affected. Additionally, in many cases courtesy and emergency announcements or messages are broadcast only through the audio portion of the system, as most display systems are not equipped to visually display courtesy announcements.
Because facilities, such as airports, may be large and may consist of multiple buildings, areas, zones or segments, such as terminals, maintaining integrity of audio systems presents challenges. Complicating the task of maintaining system integrity is that system devices, such as speakers, wiring and other networking infrastructure, including end-of-line modules, are often concealed behind or above ceilings, walls and other structures. In addition, facilities such as those mentioned above are often subject to strict fire, safety and other regulatory codes and provisions. This requires that devices and wiring used in announcement control and delivery systems meet all applicable fire and safety codes and standards, e.g., NFPA (National Fire Protection Association) standards (NFPA 72) and UL (Underwriters Laboratory) (UL864) standards.
One conventional method of monitoring system integrity is to run a separate test signal wire in addition to a primary signal wire in a return loop configuration. The system transmits a test signal on the test signal wire and monitors the return of the test signal on the return portion of the test loop circuit. Alternatively, the primary signal wire, used primarily to deliver audio signal to speakers, may be used to carry a test signal that is transmitted through the primary audio signal wire. However, a return wire or circuit must be provided to return the test signal to the system for monitoring and to confirm circuit integrity. If the system does not receive the test signal on the return side of the loop circuit, then a fault condition arises indicating that the test signal did not return and that a possible wire interruption, such as a “cut” or disconnected wire, has occurred. One problem with this approach is that often false faults arise due to the test signal wire being interrupted or disconnected rather than the primary signal wire being interrupted. Often, users may ignore the “false” fault because they continue to hear audio being delivered through some or all of the speakers. This results in a sense that the system is unreliable and that fault indications may be ignored. In addition, the return wire adds to the cost of the system and complication in the wiring scheme.